The present invention relates to methods for the production of particulate vehicles for the intravenous administration of pharmacologically active agents, as well as novel compositions produced thereby. In a particular aspect, the invention relates to methods for the in vivo delivery of substantially water insoluble pharmacologically active agents (e.g., the anticancer drug paclitaxel, the active ingredient of Taxol(trademark)). In another aspect, dispersible colloidal systems containing water insoluble pharmacologically active agents are provided. The suspended particles are encased in a polymeric shell formulated from a biocompatible polymer, and have a diameter of less than about 1 micron. Invention colloidal systems can be prepared without the use of conventional surfactant or any polymeric core matrix. In a presently preferred aspect of the invention, there is provided a method for preparation of extremely small particles which can be sterile-filtered. The polymeric shell contains particles of pharmacologically active agent, and optionally a biocompatible dispersing agent in which pharmacologically active agent can be either dissolved or suspended. Thus, the invention provides a drug delivery system in either liquid form or in the form of a redispersible powder. Either form provides both immediately bioavailable drug molecules (i.e., drug molecules which are molecularly bound to a protein), and pure drug particles coated with a protein.
Intravenous drug delivery permits rapid and direct equilibration with the blood stream which carries the medication to the rest of the body. To avoid the peak serum levels which are achieved within a short time after intravascular injection, administration of drugs carried within stable carriers would allow gradual release of the drugs inside the intravascular compartment following a bolus intravenous injection of the therapeutic nanoparticles.
Injectable controlled-release nanoparticles can provide a pre-programmed duration of action, ranging from days to weeks to months from a single injection. They also can offer several profound advantages over conventionally administered medicaments, including automatic assured patient compliance with the dose regimen, as well as drug targeting to specific tissues or organs (Tice and Gilley, Journal of Controlled Release 2:343-352 (1985)).
Microparticles and foreign bodies present in the blood are generally cleared from the circulation by the xe2x80x9cblood filtering organsxe2x80x9d, namely the spleen, lungs and liver. The particulate matter contained in normal whole blood comprises red blood cells (typically 8 microns in diameter), white blood cells (typically 6-8 microns in diameter), and platelets (typically 1-3 microns in diameter). The microcirculation in most organs and tissues allows the free passage of these blood cells. When microthrombii (blood clots) of size greater than 10-15 microns are present in circulation, a risk of infarction or blockage of the capillaries results, leading to ischemia or oxygen deprivation and possible tissue death. Injection into the circulation of particles greater than 10-15 microns in diameter, therefore, must be avoided. A suspension of particles less than 7-8 microns is, however, relatively safe and has been used for the delivery of pharmacologically active agents in the form of liposomes and emulsions, nutritional agents, and contrast media for imaging applications.
The size of particles and their mode of delivery determines their biological behavior. Strand et al. (in Microspheres-Biomedical Applications, ed. A. Rembaum, pp 193-227, CRC Press (1988)) have described the fate of particles to be dependent on their size. Particles in the size range of a few nanometers (nm) to 100 nm enter the lymphatic capillaries following interstitial injection, and phagocytosis may occur within the lymph nodes. After intravenous/intraarterial injection, particles less than about 2 microns will be rapidly cleared from the blood stream by the reticuloendothelial system (RES), also known as the mononuclear phagocyte system (MPS). Particles larger than about 7 microns will, after intravenous injection, be trapped in the lung capillaries. After intraarterial injection, particles are trapped in the first capillary bed reached. Inhaled particles are trapped by the alveolar macrophages.
Pharmaceuticals that are water-insoluble or poorly water-soluble and sensitive to acid environments in the stomach cannot be conventionally administered (e.g., by intravenous injection or oral administration). The parenteral administration of such pharmaceuticals has been achieved by emulsification of the oil solubilized drug with an aqueous liquid (such as normal saline) in the presence of surfactants or emulsion stabilizers to produce stable microemulsions. These emulsions may be injected intravenously, provided the components of the emulsion are pharmacologically inert. U.S. Pat. No. 4,073,943 describes the administration of water-insoluble pharmacologically active agents dissolved in oils and emulsified with water in the presence of surfactants such as egg phosphatides, pluronics (copolymers of polypropylene glycol and polyethylene glycol), polyglycerol oleate, etc. PCT International Publication No. WO85/00011 describes pharmaceutical microdroplets of an anaesthetic coated with a phospholipid such as dimyristoyl phosphatidylcholine having suitable dimensions for intradermal or intravenous injection.
An example of a water-insoluble drug is paclitaxel, a natural product first isolated from the Pacific Yew tree, Taxus brevifolia, by Wani et al. (J. Am. Chem. Soc. 93:2325 (1971)). Among the antimitotic agents, paclitaxel, which contains a diterpene carbon skeleton, exhibits a unique mode of action on microtubule proteins responsible for the formation of the mitotic spindle. In contrast with other antimitotic agents such as vinblastine or colchicine, which prevent the assembly of tubulin, paclitaxel is the only plant product known to inhibit the depolymerization process of tubulin, thus preventing the cell replication process.
Paclitaxel, a naturally occurring diterpenoid, has been shown to have significant antineoplastic and anticancer effects in drug-refractory ovarian cancer. Paclitaxel has shown excellent antitumor activity in a wide variety of tumor models such as the B16 melanoma, L1210 leukemias, MX-1 mammary tumors, and CS-1 colon tumor xenografts. Several recent press releases have termed Taxol(trademark), a paclitaxel formulation, as the new anticancer wonder-drug. Indeed, Taxol(trademark) has recently been approved by the Federal Drug Administration for treatment of ovarian cancer. The poor aqueous solubility of paclitaxel, however, presents a problem for human administration. Indeed, the delivery of drugs that are inherently insoluble or poorly soluble in an aqueous medium can be seriously impaired if oral delivery is not effective. Accordingly, currently used paclitaxel formulations (e.g., Taxol(trademark)) require a cremaphor to solubilize the drug. The human clinical dose range is 200-500 mg. This dose is dissolved in a 1:1 solution of ethanol:cremaphor and diluted to one liter of fluid given intravenously. The cremaphor currently used is polyethoxylated castor oil.
In phase I clinical trials, paclitaxel itself did not show excessive toxic effects, but severe allergic reactions were caused by the emulsifiers employed to solubilize the drug to form Taxol(trademark), the conventional formulation of paclitaxel. The current regimen of administration involves treatment of the patient with antihistamines and steroids prior to injection of the drug to reduce the allergic side effects of the cremaphor.
In an effort to improve the water solubility of paclitaxel, several investigators have modified its chemical structure with functional groups that impart enhanced water-solubility. Among them are the sulfonated derivatives (Kingston et al., U.S. Pat. No. 5,059,699 (1991)), and amino acid esters (Mathew et al., J. Med. Chem. 35:145-151 (1992)) which show significant biological activity. Modifications to produce a water-soluble derivative facilitate the intravenous delivery of paclitaxel dissolved in an innocuous carrier such as normal saline. Such modifications, however, add to the cost of drug preparation, may induce undesired side-reactions and/or allergic reactions, and/or may decrease the efficiency of the drug.
Protein microspheres have been reported in the literature as carriers of pharmacological or diagnostic agents. Microspheres of albumin have been prepared by either heat denaturation or chemical crosslinking. Heat denatured microspheres are produced from an emulsified mixture (e.g., albumin, the agent to be incorporated, and a suitable oil) at temperatures between 100xc2x0 C. and 150xc2x0 C. The microspheres are then washed with a suitable solvent and stored. Leucuta et al. (International Journal of Pharmaceutics 41 :213-217 (1988)) describe the method of preparation of heat denatured microspheres.
The procedure for preparing chemically crosslinked microspheres involves treating the emulsion with glutaraldehyde to crosslink the protein, followed by washing and storage. Lee et al. (Science 213:233-235 (1981)) and U.S. Pat. No. 4,671,954 teach this method of preparation.
The above techniques for the preparation of protein microspheres as carriers of pharmacologically active agents, although suitable for the delivery of water-soluble agents, are incapable of entrapping water-insoluble ones. This limitation is inherent in the technique of preparation which relies on crosslinking or heat denaturation of the protein component in the aqueous phase of a water-in-oil emulsion. Any aqueous-soluble agent dissolved in the protein-containing aqueous phase may be entrapped within the resultant crosslinked or heat-denatured protein matrix, but a poorly aqueous-soluble or oil-soluble agent cannot be incorporated into a protein matrix formed by these techniques.
One conventional method for manufacturing drug-containing nanoparticles comprises dissolving polylactic acid (or other biocompatible, water insoluble polymers) in a water-immiscible solvent (such as methylene chloride or other chlorinated, aliphatic, or aromatic solvent), dissolving the pharmaceutically active agent in the polymer solution, adding a surfactant to the oil phase or the aqueous phase, forming an oil-in-water emulsion by suitable means, and evaporating the emulsion slowly under vacuum. If the oil droplets are sufficiently small and stable during evaporation, a suspension of the polymer in water is obtained. Since the drug is initially present in the polymer solution, it is possible to obtain by this method, a composition in which the drug molecules are entrapped within particles composed of a polymeric matrix. The formation of microspheres and nanoparticles by using the solvent evaporation method has been reported by several researchers (see, for example, Tice and Gilley, in Journal of Controlled Release 2:343-352 (1985); Bodmeier and McGinity, in Int. J. Pharmaceutics 43:179 (1988); Cavalier et al., in J. Pharm. Pharmacol. 38:249 (1985); and D""Souza et al., WO 94/10980) while using various drugs.
Bazile et. al., in Biomaterials 13:1093 (1992), and Spenlehauer et al., in Fr Patent 2 660 556, have reported the formation of nanoparticles by using two biocompatible polymers, where one polymer (e.g., polylactide) is dissolved in the organic phase, together with an active component such as a drug, and the other polymer, such as albumin is used as the surface active agent. After emulsification and removal of the solvent, nanoparticles are formed, in which the drug is present inside the polymeric matrix of the polylactide particles.
The properties of the polymer solution from which the polymeric matrix is formed are very important to obtain the proper emulsion in the first stage. For example, polylactide (the polymer commonly used in the preparation of injectable nanoparticles), has a surface activity which causes the rapid adsorption thereof at the dichloromethane-water interface, causing reduced interfacial tension (see, for example, Boury et al., in Langmuir 11:1636 (1995)), which in turn improves the emulsification process. In addition, the same researchers found that Bovine Serum Albumin (BSA) interacts with the polylactide, and penetrates into the polylactide monolayer present at the oil-water interface. Therefore, it is expected, based on the above reference, that emulsification during the conventional solvent evaporation method is greatly favored by the presence of the surface active polymer (polylactide) in the nonaqueous organic phase. In fact, the presence of polylactide is not only a sufficient condition, but it is actually necessary for the formation of nanoparticles of suitable size.
Another process which is based on the solvent evaporation method comprises dissolving the drug in a hydrophobic solvent (e.g., toluene or cyclohexane), without any polymer dissolved in the organic solvent, adding a conventional surfactant to the mixture as an emulsifier, forming an oil-in-water emulsion, and then evaporating the solvent to obtain dry particles of the drug (see, for example, Sjostrom et al., in J. Dispersion Science and Technology 15:89-117 (1994)). Upon removal of the nonpolar solvent, precipitation of the drug inside the solvent droplets occurs, and submicron particles are obtained.
It has been found that the size of the particles is mainly controlled by the initial size of the emulsion droplets. In addition, it is interesting to note that the final particle size is reported to decrease with a decrease in the drug concentration in the organic phase. This finding is contrary to the results reported herein, wherein no conventional is surfactant is used for the preparation of nanoparticles. In addition, it is noted by the authors of the Sjostrom paper that the drug used, cholesteryl acetate, is surface active in toluene, and hence may be oriented at the oil-water interface; therefore the concentration of drug at the interface is higher, thus increasing the potential for precipitation.
Formation of submicron particles has also been achieved by a precipitation process, as described by Calvo et al. in J. Pharm. Sci. 85:530 (1996). The process is based on dissolving the drug (e.g., indomethacin) and the polymer (poly-caprolactone) in methylene chloride and acetone, and then pouring the solution into an aqueous phase containing a surfactant (Poloxamer 188), to yield submicron size particles (216 nm). However, the process is performed at solvent concentrations at which no emulsion is formed.
Thus it is an object of this invention to deliver pharmacologically active agents (e.g., taxanes (e.g., paclitaxel, docetaxel, and the like), and the like) in unmodified form in a composition that does not cause allergic reactions due to the presence of added emulsifiers and solubilizing agents, as are currently employed in drug delivery.
It is a further object of the present invention to deliver pharmacologically active agents in a composition of microparticles or nanoparticles, optionally suspended in a suitable biocompatible liquid.
It is yet another object of the present invention to provide a method for the formation of submicron particles (nanoparticles) of pharmacologically active agents by a solvent evaporation technique from an oil-in-water emulsion using proteins as stabilizing agents optionally in the absence of any conventional surfactants and/or in the absence of any polymeric core material.
These and other objects of the invention will become apparent upon review of the specification and claims.
In accordance with the present invention, we have discovered that substantially water insoluble pharmacologically active agents can be delivered in the form of microparticles or nanoparticles that are suitable for parenteral administration in aqueous suspension. This mode of delivery obviates the necessity for administration of substantially water insoluble pharmacologically active agents (e.g., paclitaxel) in an emulsion containing, for example, ethanol and polyethoxylated castor oil, diluted in normal saline (see, for example, Norton et al., in Abstracts of the 2nd National Cancer Institute Workshop on Taxol and Taxus, Sep. 23-24, 1992). A disadvantage of such known compositions is their propensity to produce allergic side effects.
Thus, in accordance with the present invention, there are provided methods for the formation of nanoparticles of pharmacologically active agents by a solvent evaporation technique from an oil-in-water emulsion prepared under conditions of high shear forces (e.g., sonication, high pressure homogenization, or the like), optionally without the use of any conventional surfactants and/or without the use of any polymeric core material to form the matrix of the nanoparticle. Instead, proteins (e.g., human serum albumin) are employed as a stabilizing agent.
The invention further provides a method for the reproducible formation of unusually small nanoparticles (less than 200 nm diameter), which can be sterile-filtered through a 0.22 micron filter. This is achieved by addition of a water soluble solvent (e.g., ethanol) to the organic phase and by carefully selecting the type of organic phase, the phase fraction and the drug concentration in the organic phase. The ability to form nanoparticles of a size that is filterable by 0.22 micron filters is of great importance and significance, since formulations which contain a significant amount of any protein (e.g., albumin), cannot be sterilized by conventional methods such as autoclaving, due to the heat coagulation of the protein.
In accordance with another embodiment of the present invention, we have developed compositions useful for in vivo delivery of substantially water insoluble pharmacologically active agents. Invention compositions comprise substantially water insoluble pharmacologically active agents (as a solid or liquid) coated by an optionally crosslinkable biocompatible polymer, and optionally contained within a polymeric shell. The polymeric shell is a crosslinked biocompatible polymer. The polymeric shell, containing substantially water insoluble pharmacologically active agents therein, can then be suspended in a biocompatible aqueous liquid for administration.
The invention further provides a drug delivery system in which part of the molecules of pharmacologically active agent are bound to the protein (e.g., human serum albumin), and are therefore immediately bioavailable upon administration to a mammal. The other portion of the pharmacologically active agent is contained within nanoparticles coated by protein. The nanoparticles containing the pharmacologically active agent are present as a substantially pure active component, without dilution by much, if any, polymeric matrix.
A large number of conventional pharmacologically active agents circulate in the blood stream bound to carrier proteins (through hydrophobic or ionic interactions) of which the most common example is serum albumin. Invention methods and compositions produced thereby provide for a pharmacologically active agent that is xe2x80x9cpre-boundxe2x80x9d to a protein (through hydrophobic or ionic interactions) prior to administration.
The present disclosure demonstrates both of the above-described modes of bioavailability for paclitaxel, an anticancer drug capable of binding to human serum albumin (see, for example, Kumar et al., in Research Communications in Chemical Pathology and Pharmacology 80:337 (1993)). The high concentration of albumin in invention particles, compared to Taxol(trademark), provides a significant amount of the drug (i.e., paclitaxel) in the form of molecules bound to albumin, which is also the natural carrier of the drug in the blood stream.
In addition, advantage is taken of the capability of human serum albumin to bind paclitaxel, as well as other drugs, which enhances the capability of paclitaxel to absorb on the surface of the particles. Since albumin is present on the colloidal drug particles (formed upon removal of the organic solvent), formation of a colloidal dispersion which is stable for prolonged periods is facilitated, due to a combination of electrical repulsion and steric stabilization.
In accordance with the present invention, there are also provided submicron particles in powder form, which can easily be reconstituted in water or saline. The powder is obtained after removal of water by lyophilization. Human serum albumin serves as the structural component of invention nanoparticles, and also as a cryoprotectant and reconstitution aid. The preparation of particles filterable through a 0.22 micron filter according to the invention method as described herein, followed by drying or lyophilization, produces a sterile solid formulation useful for intravenous injection.
The invention provides, in a particular aspect, a composition of anti-cancer drugs, e.g., paclitaxel, in the form of nanoparticles in a liquid dispersion or as a solid which can be easily reconstituted for administration. Due to specific properties of certain drugs, e.g., paclitaxel, such compositions cannot be obtained by conventional solvent evaporation methods that rely on the use of surfactants. In the presence of various surfactants, very large drug crystals (e.g., size of about 5 microns to several hundred microns) are formed within a few minutes of storage, after the preparation process. The size of such crystals is typically much greater than the allowed size for intravenous injection.
While it is recognized that particles produced according to the invention can be either crystalline, amorphous, or a mixture thereof, it is generally preferred that the drug be present in the formulation in an amorphous form. This would lead to greater ease of dissolution and absorption, resulting in better bioavailability.
In accordance with another embodiment of the present invention, there are provided various methods of administering a pharmacologically active agent which must be administered in multiple doses over a cycle time which is less than the cycle time of administration of non-invention formulations of the pharmacologically active agent.
The invention further provides various methods of reducing the myelosuppressive effects and/or the neurotoxic effects of a pharmacologically active agent administered to a patient in need thereof.
In accordance with yet another embodiment of the present invention, there are provided methods of administering pharmacologically active agent(s) to a patient having a disease capable of treatment by the pharmacologically active agent(s). Invention methods comprise administering formulations according to the invention containing suitable pharmacologically active agent(s) to the patient. Diseases contemplated for treatment according to the invention include cancers, proliferative diseases, and the like. Administration of invention formulations can be accomplished in a variety of ways, e.g., intravenous or intraarterial, and/or can be without the use of steroids and/or cytokines, and/or can be in combination with a biochemotherapy agent; and/or the single dose levels of pharmacologically active agents can be greater than about 50 mg; and/or the cumulative dose levels of pharmacologically active agents can be greater than about 250 mg/m2 every 3 weeks.
In accordance with a further embodiment of the present invention, there are provided methods of delivering a pharmacologically active agent to a localized area of a patient for sustained release of the pharmacologically active agent over an extended period of time (e.g., from about 1 day to about 1 year). Invention methods comprise administering to the patient a suitable pharmacologically active agent in the invention formulation, wherein the invention formulation has been dispersed within a matrix of suitable biocompatible material.
In accordance with yet another embodiment of the present invention, there are provided methods of orally administering pharmacologically active agent(s) to a patient in need thereof. Invention methods comprise orally administering an invention formulation of the pharmacologically active agent(s) in combination with intestinal cell efflux inhibitor(s).
In accordance with still another embodiment of the present invention, there are provided methods of administering a combination of suitable pharmacologically active agent(s) to a patient in need thereof. Invention methods comprise administering to the patient 25-75% of the conventionally effective dosage level of each of the suitable pharmacologically active agent(s) in the invention formulation.